A problem affecting the health and safety of a variety of workers is that of providing a safe, non-slippery, dry area upon which the workers can stand. Hospital operating room personnel are routinely required to stand and work in conditions in which the floor is inundated with several liters of blood, bodily fluids, and saline or other solutions during a single procedure. The abundance of fluids released during surgery is due in part to refinements and widespread implementation of improved surgical techniques during recent years.
In U.S. Pat. No. 4,635,913, issued Jan. 13, 1987; U.S. Pat. No. 4,718,653, issued Jan. 12, 1988; and U.S. Pat. No. 4,811,937, issued Mar. 14, 1989, Rothman disclosed a series of Portable Surgical Drainage Platforms. The inventions he developed could assist surgeons and other surgical staff by supporting the personnel on grating and removing liquid that falls through the grating. The platforms are, however, rather heavy and are also difficult to sterilize, especially in the limited amount of time that may be available between surgeries.
LaRooka received U.S. Pat. No. 4,243,214 on Jan. 6, 1981, for her Irrigation-Debridement-Repair Caddy. That disclosure is directed to an apparatus that can be placed under an extremity of a person during a surgical procedure. The Irrigation-Debridement-Repair Caddy is designed to collect some of the irrigation distending medium and excised tissue that would otherwise drip onto the floor and collect the fluid in a closeable bottle for eventual disposal.
Other devices such as the AquaVac mat marketed by Arthroplastics of P.O. Box 332 Chagrin Falls, Ohio 44022 appear to be directed primarily toward removing water from floors rather than quantifying the amount of fluid received from a patient in order to determine whether the patient's condition is satisfactory.
Clear saline solution or nonelectrolytic distending medium infused into the region where surgery is being conducted allows the surgeon to see the affected tissue much more clearly than would otherwise be possible. In addition, the distending medium can separate and stabilize the tissue to improve surgical precision and reduce the time required to carry out procedures.
Among the problems engendered by dispersal of infused fluids and blood onto operating room tables and floors are the considerable inconvenience to workers, the increased likelihood of contamination, the potential for spread of infectious disease, More importantly, distending medium is used in hysteroscopic, urologic, and possibly other surgical procedures that, if taken up by the patient, increase risk of complications. A patient can suffer serious, or even fatal, complications by absorption of distending medium that is suffused into the area where the surgery is conducted by the hysteroscope. The amount of distending medium that a patient can absorb without intolerably dangerous adverse effects is related in non-intuitive ways to various individual physical, chemical, and other factors. The perioperative nurse will, before the patient arrives in the operating room, make a reasonable estimate of the amount of distending medium that a specific patient can tolerably absorb by factoring the person's age, weight, fitness, hormonal balance, the formulation of the distending medium, the procedure being performed, and a host of other variables. Unfortunately, the maximum usefulness of that estimate can be realized only if the amount of fluid the patient retains can be timely determined with sufficient accuracy while the procedure is carried out.
The quantity of infusion fluids absorbed by a patient naturally increases with the length of time required to perform the procedure. Hospitals, surgeons, and patients normally seek to conclude the surgery as quickly as possible for good reasons. Other things being equal, the less time required to perform a surgery, the better the expected outcome and the quicker the patient is expected to recover.
Infusion fluids are taken up by the patient more rapidly during some procedures, compared to others. Sometimes infusion fluids are absorbed so rapidly that the surgeon may not have enough time to address and correct all of the problems and complexities discovered during the surgery. In such instances, it might be necessary to terminate a procedure when only a few additional minutes of the surgeon's time would be sufficient to complete the process as desired. That is a very undesirable situation because patients in those cases must be allowed to recover in the hospital for several days and then, often in a weakened condition, again be prepared, anesthetized, and the surgery resumed. Because those additional risks are widely recognized, as is the risk of continuing a surgery when a patient may, or may not, be in danger from excessive absorption of infusion fluids, the surgeon, lacking accurate information, is forced to make a decision that can easily be criticized in hindsight.
Based on these factors, it is easy to understand that surgeons, hospitals, and their patients would be greatly assisted by more accurate knowledge of the amount of infusion fluids retained by surgical patients. Although infusion fluids may accumulate in the abdomen or the patients extremities, the greatest concern is for accumulation and absorption of infusion fluids during surgeries in which severed veins are exposed to infusion fluids. Hysteroscopic and, to a lesser extent, urologic procedures performed using monopolar electrosurgery inherently give rise to conditions that can quickly lead to dangerous complications if any member of the surgical team is unable to maintain a vigilant lookout for the onset of hyponatremia.
The hazards of hyponatremia are widely recognized by workers throughout the fields of obstetrics and gynecology. Although the medical literature has many excellent publications addressing the problem in varying breadth and depth, a good overview explaining the subject and the causation of the potential harms is presented by Donna Morrison, R.N. in her article “Management of Hysteroscopic Surgery Complications,” J. Assoc. of Operating Room Nurses, vol. 69, No. 1, Jan. 1999, pp.□194-209. Morrison explains that dilutional hyponatremia is a complication of hysteroscopic surgery that is associated with intravasation of a low viscosity nonelectrolytic distending medium. Women are more likely than men to suffer dilutional hyponatremia, and premenopausal women are 26 times more likely than postmenopausal women to encounter hyponatremia. Premenopausal women are at greatest risk, then, usually as the result of hysteroscopic procedures; the same considerations are, however, important in urologic, and perhaps other procedures that may be undertaken on either male or female patients. For the convenience of the reader, it is to be understood that references to hysteroscopy and hysteroscopic procedures are intended to include urology, urologic, and urological procedures, and any other type of surgical procedure that exposes the patient to risk of hyponatremia or in which it would be helpful to know the volume of fluid retained by a patient.
The distending medium, or infusion fluid used in electrosurgery has lower osmotic potential, or tonicity, than the patient's tissues, serum, and intercellular fluids. For that reason, the distending medium is absorbed fairly quickly by the tissues surrounding the surgical site. Not only is the distending medium absorbed quickly by osmosis, the fluid is supplied under pressure in order to distend the area where the surgery is being performed to enable the surgeon to repair damaged tissue with greater speed and precision. The pressure needed to distend the area can exceed the patient's blood pressure thereby actively forcing distending medium to flow into blood veins that are cut or broken in the course of the surgery. Free water can enter the vascular system through blood vessels and sinuses opened as the integrity of the endometrial lining or other tissue is interrupted during surgery.
Efforts to cauterize exposed vasculature are maintained throughout the surgery, however the process is not instantaneous, and some distending medium will be forced into the patient's circulatory system as a result. The duration of the surgery must be limited for that reason, even under the best of circumstances. As a practical matter, undetected damage to vessels or other tissue exposed to the pressurized distending medium will sometimes be present, vasculature thought to have been cauterized may subsequently begin to admit distending medium, or other sub-optimal conditions may develop. Any event or condition that increases the patient's uptake of distending medium necessarily shortens the permissible duration of the surgical procedure.
If that were the extent of the problem, a patient in that situation might merely need to endure a period of uncomfortable puffiness. However, the brain, like the rest of the patient's tissue, seeks to balance the ionic strength of the diluted blood by removing water from the blood and adding that water to the brain tissue. The skull provides scant room for the brain to expand as it swells from the added water; extreme pressure can build fairly quickly. Brain stem herniation can develop as the brain expands attempting to equalize interstitial and intervascular osmotic pressures. Morrison reports that this condition, hyponatremic encephalopathy, has high morbidity and mortality rates and may result if dilutional hyponatremia is not recognized at its onset and treated promptly. She, like many other observers of the problem, recommends that operating room personnel regularly monitor the amount of distending medium the patient receives and the amount returned because that is the quickest way to detect possible intravasation caused dilutional hyponatremia.
To that end, surgeons often request the operating room personnel to report the amount of fluid that has been introduced into and received from the patient. Fluid limits are normally fixed between 500 ml and 1,500 ml., and surgery time is frequently limited to one hour. Unfortunately, it is difficult to reliably measure the volume of distending medium received from the patient using traditional methods and equipment. Likewise, It is difficult to measure the volume of fluid infused with traditional methods and equipment.
Operating room personnel will know with certainty the number of 3 liter bags of distending medium that have been infused at any particular time. Beyond that, there has been little certainty available. To estimate the amount remaining in a partially used 3 liter container of distending medium, it is usually necessary to remove the bag from the pressurizing cuff or collar in which it is located during use. Of course, removing the pressurizing collar halts the flow of distending medium to the location of the surgery which can quickly interrupt the conduct of the procedure. Once the uncalibrated, shapeless 3 liter bag is visible, operating room personnel would then estimate (i.e. guess at) the amount remaining in it. The amount of infusion fluid discharged from the hysteroscope outflow would normally be collected, and therefore measurable. Careful draping can direct some of the returned fluid into kick buckets, but some is likely to disperse onto the operating room floor, the table, and into pads or towels. The difference between the amount of fluid introduced and the amount of fluid collected or dispersed onto the operating table and floor gives some estimation of the amount of fluids remaining in the patient. Such estimates are crude approximations at best, and generally recognized as such by the persons making and using them.
A cross check may be provided by measuring serum sodium concentration during the surgery both periodically and whenever intravasation is suspected.
If the surgical team discovers that intravasation has occurred, the situation must be treated as an emergency requiring the surgeon to halt the procedure as soon as it is safe to do so. Electrolytes, oxygen, and other treatments would be administered as quickly as possible.
It is readily appreciated that the consequences of underestimating the amount of infused fluid taken up by the patient can include morbidity and mortality. Underestimating the amount of fluid received from the patient can result in premature termination of surgery and can instigate an emergency response that imposes additional risk upon the patient.
In an effort to determine the reliability of the estimates of fluid balance that operating room personnel make, a preliminary test was conducted by one hospital to evaluate the accuracy of visual estimates of fluid volumes experimentally. Four experienced operating room nurses were each asked to visually estimate fluid volumes under nineteen different conditions: the amount of distending medium remaining in ten different 3 liter bags; the amount of fluid received in four different kick buckets; and the volume of fluid present on five different operating room floors. The results of the experiment are presented in Table 1. Although the individuals were experienced, trained, and capable in their fields, their estimates of fluid volumes deviated from the actual amounts sufficiently to risk premature cessation of a surgical procedure in most instances. Participants underestimated the amount of fluid present regularly. Out of 76 estimates 74 were less than, and only two exceeded, the actual liquid volume. The errors are additive, and effect of the cumulative errors is that, even if only the best estimate from each trial is considered, in more than 75% of the cases, a recommendation to halt the surgery is indicated by these estimates, even if absolutely no distending medium had been retained by the patient.
In the effort to more accurately evaluate the amount of distending medium returned by the patient, surgical drapes may be arranged to direct the returned fluid to buckets positioned on the floor. It can be necessary to halt the surgery while the unsterile contents of the buckets are measured. But, as can be seen from studying Table 1, the estimation errors for the amounts of fluid on the operating table and on the floor can be so large that there is little value in knowing the volume of fluid accumulated in the kick buckets.
What is needed is a practical way to collect fluids returned from a patient during hysteroscopic surgical procedures.
Also needed is a way to measure the volume of fluids returned from a patient during hysteroscopic surgery.
A further need is for apparatus whereby it is possible to determine the volume of distending medium that has been infused into a patient.
Yet another need is for the ability to quickly learn the difference between the amount of distending medium that has been infused into the patient and the amount of distending medium that has been returned from the patient.